Spaghetti worms are a marine relative of the earthworm, growing up to 15 cm in length. These worms have long, cylindrical bodies that are divided into many similar sections called segments. Some structures, like muscles, kidneys, and nerves are repeated in each segment. Body segments have appendages on each side which have small bristles protruding. They have many long tentacles radiating from the head, close to the mouth, which are used for finding and collecting food. Tentacles may be up to 1 m long (100 cm).
Spaghetti worm tentacles are grooved and lined with hair-like cilia that help collect and transport food to the mouth. Food that drop on the tentacles are carried down the groove and to the hidden mouth. Larger food particles are lassoed by the elastic tentacles and dragged to the mouth. The elastic tentacles can be withdrawn if necessary and can regenerate if broken or eaten by predators. Some species of butterflyfish eat spaghetti worm tentacles.
Most spaghetti worms live in burrows or crevices and construct tubes for themselves from sand and gravel which they cement together with a mucus-like secretion from a gland close to the mouth. Spaghetti worms generally do not leave their tube or reef crevices and are considered sedentary worms. The use their bristles to move up and down inside their tube.